I was engineer #1 and CTO for a SaaS analytics start-up. It was pretty obvious after 2 years that there was no Product Market Fit. The CEO/Investor was OK with losing 900k/year so he wanted to keep going. I negotiated away my equity for high pay and an expense account. But I still quit 2 years later because the wheels were coming off as the sales pipeline dried up and the lead sales person was trying to sign anything, even work that he knew we couldn't do without taking a big loss when the engineering effort was factored in.
At a small company you would ideally have engineering involved before any contracts were signed.
At a large company you generally pass the sale off to a integration team who isn't commission based. And that team will quickly find out if the customer was badly lied to, And you will have time to cancel the commission.
